Monitor Globally, Manage Locally

About seven or eight years ago, running a wide area data network was actually
a little easier than it is today. Most of that simplicity goes out the window
with modern applications, especially those incorporating voice and video. In
those cases, detailed application analysis and network planning is a must. Connecting
to a VPN or the Internet makes it even more complicated, because you can have
random network paths between sites, variable network latency, packet loss and
the overhead associated with encryption. Multi-protocol, label-switching networks
add to the complexity, as you have to make decisions about queues, classes and
quality of service.

Shunra provides a comprehensive suite of management and monitoring tools designed to address network management and application performance challenges. They have a high-end product set based around an intelligent appliance (Shunra Enterprise), and a lower-end, software-only product.

More Than a Traffic Cop
The Shunra appliance does more than simply monitor traffic. You can also use
it to test and simulate network issues such as packet loss, latency, out of
order packet arrival and other factors. With the appliance installed in your
production or lab network, you can launch applications, test scripts, and evaluate
the impact of network degradation and congestion on actual or simulated network
traffic.

Shunra’s simulation and modeling tools are its greatest strengths. You can purchase script-based modeling tools, but this one has a friendly Microsoft Visio interface. So rather than learning a scripting product, you can “draw” your network and test it from the drawing in real time. You can also integrate third party tools like Mercury LoadRunner into your test and modeling program.

Installation was fairly straightforward. I plugged my “console” laptop into the management port, and the input and output of my network into the Ethernet ports. The easy-to-read product manuals include helpful diagrams and accurate, up-to-date information. It’s a good thing, too, because when I tried jamming in disks and plugging in cables without consulting the documentation, I didn’t get very far.

Once the system was completely installed and connected, I fired up the StormCatcher
and StormAppliance Management utility. Seeing as it was Friday night, I fired
up my favorite Internet radio station to use as a real-world streaming traffic
source. It ran perfectly on my high-end cable service (which runs at greater
than 3mbps) at the 20kbps UDP stream rate on my Windows 2000 system. The traffic
was duly captured by StormCatcher, which I had installed between my network
hub and the streaming laptop.

Next, I selected the higher fidelity 32kbps stream rate to stress the connection a bit further. No surprise, this didn’t work quite as well and I experienced somewhat choppy audio playback (see Figure 1). After those tests, it seemed that StormCatcher was using ICMP traffic (pings) for analysis.

If this had been a real business application (like a CEO’s audio or video broadcast), the call would have gone out to fix the problem or at least identify the cause of the dropouts. In most corporate applications, though, you’ll have direct control of your network’s end points. Using the network simulation and modeling tools can help you to find the solution either directly or by ruling out certain factors.

Testing, Testing
Creating a model of my part of the network was simple. On the left side, I started
with a port, then added a gateway (to allow bandwidth modifications) and a WAN
cloud. Then I did the same thing for the other side. Simply drag and drop the
symbols from the palette. The only tricky part was that the link elements have
to touch the “X” on the ports and other network components. The diagram shows
a red flash to indicate that you’ve established continuity. Then you can go
to the Shunra/ Storm menu and select “test” to test the model you’ve built (see
Figure 2).

Figure 2. A diagram of my test network created with the Shunra modeling tool. (Click image to view larger version.)

After an initial test, you can start varying network bandwidth and other factors, simulating all sorts of network effects and issues. In this UPD/streaming example, I added 180 ms latency to simulate a transoceanic link. I had no problems with my 20k stream. Then I stopped the tool, increased the packet loss and re-ran the model. The music stopped.

On file transfer applications or chatty client/server applications, latency has a dramatic impact. Acknowledgements end up coming back over a slow return path. Even well-known standard protocols like NTP and Microsoft CIFS can be quite chatty. I started a 30MB file transfer as a test, and throughput slowed to a crawl when I cranked up the latency.

In a lot of cases, you can use rules of thumb and simple math to design networks. However, this falls apart if you’re pressed to provide detailed predictions based on real data.

The Shunra tool set lets you take real or simulated traffic, adjust the parameters and answer with solid data whether more bandwidth will fix the slow response time on that new homegrown application you just rolled out over your WAN. You can run some advanced tests to study the impact of factors like queuing delays, routing behavior, MPLS and even IPV6.

The $40,000 price tag reflects Shunra’s sophisticated functionality as a network monitoring, predictive modeling and testing platform. It also reflects the vast sums you can save by having an efficiently designed global network.

Shunra also sells a lower-cost Desktop version of the package, which installs as a software client and works with Windows device drivers to deliver network capture and traffic degradation functions. The Desktop version worked like the appliance, but lacked the depth of options and fine level of granularity. If you were trying to work on testing applications under degraded conditions, you might be OK, but the full appliance solution set seems to have a lot of nice features and capabilities, and the ability to simulate complex routing and MPLS conditions.

The Shunra Suite, or even the Desktop package, are a "must have" if you're
designing you own wide-area networks, or develop and deploy custom applications
that will eventually run over a WAN. The costs involved in otherwise trying
to tune homegrown applications to run well over a WAN might just allow the system
to pay for itself.